Dr. James Thomka
My research falls within the broad fields of paleontology and stratigraphy, with an emphasis on deep-time interactions between organisms and their physical environment. This encompasses studies into the biology, ecology, and preservation of fossil organisms and communities (as well as modern counterparts where appropriate); studies of trace fossils and sedimentary characteristics of the units containing fossil assemblages; and studies of the stratigraphic relationships between relevant intervals of the geologic record. Results from these analyses form the framework for interpretation of broader linkages between the biosphere and climatic-oceanographic-tectonic systems.
I have engaged in research into nearly all forms of ancient life, including microorganisms, plants, trace fossils, macroinvertebrates, and vertebrates. My students and I have been particularly active in pursuing the following research areas:
(1) Preservation of fossil echinoderms, including applications of crinoid taphonomy, ‘cystoid’ taphonomy, and echinoid taphonomy to paleoenvironmental reconstruction and facies analysis. Conditions responsible for exceptional preservation of echinoderm assemblages have also been heavily investigated.
(2) Parasite-host and predator-prey dynamics in the fossil record, focusing on the patterns of host-specificity among pit-forming parasites on stalked echinoderms, frequencies of skeletal regeneration of echinoderms following predatory attacks, and evolutionary changes induced by such interactions.
(3) Ecology and preservation of organisms encrusting hard substrates, with an emphasis on interpreting the functional morphology and sedimentological significance of attachment structures. Sea-level controls on the development of biological buildups (reefs, bioherms, biostromes, etc.) are a related area of study.
(4) Patterns of marine authigenesis, particularly the stratigraphical, geochemical, and preservational importance of concretions, hardground surfaces, and indicators of early diagenetic mineralization. Siderite (FeCO3) concretions, including examples containing spectacularly preserved fossil material, are a frequent subject of study.
(5) Trace fossils (ichnofossils) as sources of information in sedimentology, stratigraphy, and paleoecology. Research has focused on using information derived from trace fossils to improve interpretations of depositional environments, relative sea-level changes, and biotic interactions.
(6) Global climatic/oceanic instability and associated biological turnover during the Late Ordovician through middle Silurian. This includes integration of sequence stratigraphic, stable isotopic, magnetic susceptibility, and paleontological datasets.
I make a concerted effort to include students in my research, and remain active in supervising undergraduates who are interested in paleontology and sedimentary geology both as independent studies and as part of Honors College theses. I encourage you to contact me if you would like to hear more about opportunities to advance science through original research!
100: Earth Science
101: Introductory Physical Geology
102: Introductory Historical Geology
105: Geology for Engineers
122: Mass Extinctions and Geology
453/553: Geology Field Camp I
(*asterisk denotes supervised undergraduate student co-author)
Thomka, J.R., and *Eddy, D.B., under review, Repeated regeneration of crinoid spines in the Upper Pennsylvanian of eastern Ohio: Evidence of elevated predation intensity and significance for predator-driven evolution of crinoid morphology: Palaios, v. 33.
Thomka, J.R., Brett, C.E., and *List, D.A., under revision, Magnetic susceptibility of the latest Telychian-early Sheinwoodian (middle Silurian) succession of southeastern Indiana and northern Kentucky: Implications for stratigraphic interpretation of diagenetically altered units: Palaeogeography, Palaeoclimatology, Palaeoecology, v. 522.
Thomka, J.R., under revision, An additional example of the ichnogenus Zoophycos in Cambrian strata (Gallatin Formation; Wyoming, USA): Palaeoworld, v. 27.
Brett, C.E., Hartshorn, K.R., Waid, C.B.T., McLaughlin, P.I., Bulinski, K.V., Thomka, J.R., and Paton, T.R., in press, Lower to middle Paleozoic stratigraphy in the greater Louisville, Kentucky area: Geological Society of America Field Trip Guidebooks, v. 51.
Thomka, J.R., in press, Plant or animal, terrestrial or marine? Thoughts on specimen curation in university palaeontological teaching collections based on an example from Ohio, USA: The Geological Curator, v. 10.
Thomka, J.R., Brett, C.E., *Bole, T.A., and Campbell, H.J., in press, A noteworthy accumulation of disparid crinoids from the type Cincinnatian (Upper Ordovician) of Ohio, USA: Implications for the palaeoecology and taphonomy of crinoid “logjam” assemblages: Swiss Journal of Palaeontology, v. 137.
Thomka, J.R., and *Eddy, D.B., 2018, Notes on additional material associated with the type specimens of Diphuicrinus ohioensis (Echinodermata: Crinoidea) from the Middle Pennsylvanian of southeastern Ohio: Ohio Journal of Science, v. 118, p. 25-30.
Thomka, J.R., Sullivan, N.B., and Brett, C.E., 2018, Arthrophycus as a mimic of crinoid column impressions in the Lower Silurian of central Kentucky, USA: Lethaia, v. 51, p. 96-101.
Thomka, J.R., and Brett, C.E., 2017, Insights into the taxonomy and paleoecology of the ‘bead bed’ crinoid (Echinodermata: Crinoidea) based on new material from the Lower Silurian Brassfield Formation of east-central Kentucky: Palaios, v. 32, v. 762-768.
Brett, C.E., and Thomka, J.R., 2017, Fossil echinoderms of the middle Silurian in North America: An age of crinoids and “anachronistic” faunas: Mid-American Paleontological Society Exposition Digest, v. 40, p. 97-126.
Thomka, J.R., and Brett, C.E., 2017, The holdfast of Finitiporus boardmani (Echinodermata: Diploporita) in the Silurian Massie Formation of the Cincinnati Arch region, USA: Swiss Journal of Palaeontology, v. 136, p. 365-368.
Deline, B., and Thomka, J.R., 2017, The role of preservation on the quantification of morphology and patterns of disparity within Paleozoic echinoderms: Journal of Paleontology, v. 91, p. 618-632.
Sullivan, N.B., McLaughlin, P.I., Brett, C.E., Cramer, B.D., Kleffner, M.A., Thomka, J.R., and Emsbo, P., 2016, Sequence boundaries and chronostratigraphic gaps in the Llandovery of Ohio and Kentucky: The record of Early Silurian paleoceanographic events in east-central North America: Geosphere, v. 12, p. 1813-1832.
Thomka, J.R., Bantel, T.E., and *Tomin, M.J., 2016, Unusual preservation of the trace fossil Conostichus in middle Silurian carbonate facies of Indiana, USA: Canadian Journal of Earth Sciences, v. 53, p. 802-807.
Aucoin, C.D., Brett, C.E., Dattilo, B.F., and Thomka, J.R., 2016, Sequence stratigraphic model for repeated “butter shale” Lagerstätten in the Ordovician (Katian) of the Cincinnati, Ohio region, USA: Canadian Journal of Earth Sciences, v. 53, p. 763-773.
Thomka, J.R., Brett, C.E., *Young, A.L., Bantel, T.E., and Bissett, D.L., 2016, Taphonomy of ‘cystoids’ (Echinodermata: Diploporita) from the Napoleon quarry of southeastern Indiana, USA: The Lower Silurian Massie Formation as an atypical Lagerstätte: Palaeogeography, Palaeoclimatology, Palaeoecology, v. 443, p. 263-277.
Brett, C.E., Thomka, J.R., Schwalbach, C.E., Aucoin, C.D., and Malgieri, T.J., 2015, Faunal epiboles in the Upper Ordovician of north-central Kentucky: Implications for high-resolution sequence and event stratigraphy and recognition of a major unconformity: Palaeoworld, v. 24, p. 149-159.
Thomka, J.R., and Brett, C.E., 2015, Palaeontological and sedimentological effects of micro-bioherms in the Middle Silurian Massie Formation of southeastern Indiana, USA: Lethaia, v. 48, p. 172-187.
Brett, C.E., Malgieri, T.J., Thomka, J.R., Aucoin, C.D., Dattilo, B.F., and Schwalbach, C.E., 2015, Calibrating water depths of Ordovician communities: Lithological and ecological controls on depositional gradients in Upper Ordovician strata of southern Ohio and north-central Kentucky, USA: Estonian Journal of Earth Sciences, v. 64, p. 19-23.
Thomka, J.R., and Brett, C.E., 2015, Paleoecology of pelmatozoan attachment structures from a hardground surface in the middle Silurian Massie Formation, southeastern Indiana: Palaeogeography, Palaeoclimatology, Palaeoecology, v. 420, p. 1-12.
Thomka, J.R., Malgieri, T.J., and Brett, C.E., 2014, A swollen crinoid pluricolumnal from the Upper Ordovician of northern Kentucky, USA: The oldest record of an amorphous paleopathologic response in Crinoidea?: Estonian Journal of Earth Sciences, v. 63, p. 317-322.
Thomka, J.R., and Brett, C.E., 2014, Taphonomy of diploporite (Echinodermata) holdfasts from a Silurian hardground, southeastern Indiana, United States: Palaeoecologic and stratigraphic significance: Geological Magazine, v. 151, p. 649-665.
Thomka, J.R., and Motz, G.J., 2014, First report of Silurian crinoid columnals with tetralobate and hexalobate lumen structures: GFF, v. 136, p. 266-269.
Brett, C.E., Thomka, J.R., Sullivan, N.B., and McLaughlin, P.I., 2014, Anatomy of a compound sequence boundary: A basal Silurian karstic unconformity in the Cincinnati Arch region: GFF, v. 136, p. 42-47.
Thomka, J.R., and Brett, C.E., 2014, Diploporite (Echinodermata, Blastozoa) thecal attachment structures from the Silurian of southeastern Indiana: Journal of Paleontology, v. 88, p. 179-186.
Thomka, J.R., and Lewis, R.D., 2013, Siderite concretions in the Copan crinoid Lagerstätte (Upper Pennsylvanian, Oklahoma): Implications for interpreting taphonomic and depositional processes in mudstone successions: Palaios, v. 28, p. 697-709.
Brett, C.E., and Thomka, J.R., 2013, Fossils and fossilisation: eLS: Citable Reviews in the Life Sciences, 12 p.
Brett, C.E., Cramer, B.D., McLaughlin, P.I., Kleffner, M.A., Showers, W.J., and Thomka, J.R., 2012, Revised Telychian-Sheinwoodian (Silurian) stratigraphy of the Laurentian mid-continent: Building uniform nomenclature along the Cincinnati Arch: Bulletin of Geosciences, v. 87, p. 733-753.
Thomka, J.R., Mosher, D., Lewis, R.D., and Pabian, R.K., 2012, The utility of isolated crinoid ossicles and fragmentary crinoid remains in taphonomic and paleoenvironmental analysis: An example from the Upper Pennsylvanian of Oklahoma, United States: Palaios, v. 27, p. 465-480.
Thomka, J.R., Lewis, R.D., Mosher, D., Holterhoff, P.F., *León y León, I.A., and Pabian, R.K., 2011, Microstratigraphy and comparative taphonomic analysis of the upper core shale of a Pennylvanian cyclothem: Keys to the recognition of subtle cyclic deposition: Gulf Coast Assocation of Geological Societies Transactions, v. 61, p. 463-481.
Thomka, J.R., Lewis, R.D., Mosher, D., Pabian, R.K., and Holterhoff, P.F., 2011, Genus-level taphonomic variation within cladid crinoids from the Upper Pennsylvanian Barnsdall Formation, northeastern Oklahoma: Palaios, v. 26, p. 377-389.
Thomka, J.R., and Marzen, L.J., 2009, Treefall evidence for high wind events at Hawn State Park, St. Francois Mountains, Missouri: A case study in selective field data collection: Papers of the Applied Geography Conferences, v. 32, p. 173-180.
PhD, 2015, University of Cincinnati (Cincinnati, Ohio)
- Dissertation: Dynamic Linkages between Stratigraphy, Climate, Oceanography, and Biotic Events in the Middle Silurian of Eastern Laurentia
MS, 2010, Auburn University (Auburn, Alabama)
- Thesis: Genesis and Taphonomy of a Crinoid Lagerstätte in the Upper Pennsylvanian Barnsdall Formation of Northeastern Oklahoma
BS, 2008, University of Tennessee—Martin (Martin, Tennessee)
- Thesis 1: Siderite Concretions of the Upper Cliff Coal Interval (Pennsylvanian: Westphalian A): Fossil Content and Paleoenvironmental Implications
- Thesis 2: Diagenesis and Morphology of Unusual Stromatolites in the Upper Cambrian Copper Ridge Dolomite, Cherokee Lake, East Tennessee